I am on a small network with 23 users using mixed operating systems. 8 of the computers use Windows XP and the other 15 are on Windows 7. There is only one domain controller which is Server 2008 R2. The domain controller is our file, certificate, DHCP, and AD server. Three weeks ago an issue started occurring where network activity would stop for brief periods of 4 to 7 seconds of time at random times over the course of each business day. Not a big delay but when people are accessing databases and the TCP randomly drops, then my life becomes a nightmare.Last night we left all of the computers on and working on various things to see if there was a load issue. Everything ran like a dream for almost four hours until we decided we were done testing. We turned off one computer and network communications stalled. We turned it back on and got all of the computers running the database that stalled out back up. We determined that if any network computer was turned off on the network communication for all other computers would cease for 4-7 seconds.
What we have tried
We changed out the cables on the servers (they were old) to the switches
We replaced the switches (they were even older) with new Gigabit switches
Wiresharked a few PCs and the server to try and see where the failures are happening.
Turning everything on and running as many items as possible to see if the load is killing us.